1. Field of the Invention
The present invention relates to an ultrasonic endoscope arranged with an ultrasonic transducer and an endoscopic viewing section at the distal end of an insertion portion to be inserted in a body cavity, and more particularly to an ultrasonic endoscope adapted to fit a balloon on the ultrasonic transducer.
2. Description of the Related Art
The ultrasonic endoscope has an insertion portion to be inserted in a body cavity. The insertion portion has a distal hard portion incorporating ultrasonic examining means and endoscopic viewing means therein. The endoscopic viewing means is made up with an illuminating device and a viewing device. The viewing device usually has a solid-state imager. Meanwhile, the ultrasonic examining means is made up by an ultrasonic transducer. The ultrasonic transducer is to transmit an ultrasonic wave toward a body interior and receive a reflection echo from a tissue laminagraphic point, thereby acquiring information about a body-interior tissue. The ultrasonic transducer is to make a scanning mechanically or electronically over a predetermined range, thereby allowing diagnosis, e.g. finding out a diseased point in the body interior.
Here, conspicuous attenuations are encountered through air in the ultrasonic signal sent from the ultrasonic transducer into a body interior and in the reflection echo of from a laminagraphic point of a body-interior tissue. In order to interpose an ultrasonic transmission medium between the ultrasonic transducer and the wall of a body cavity, a balloon is fit on the distal hard portion where the ultrasonic transducer is arranged. The balloon is filled therein with an ultrasonic transmission medium and inflated a predetermined amount under the pressure thereof. By placing the balloon in abutment against a body-cavity wall, air is prevented from existing along the transmission and reception paths of an ultrasonic wave.
Here, when confirmed a presence of a point assumed as a diseased as a result of the ultrasonic examination, tissue cells are sampled out of the point by use of a needle tool, thereby conducting an exact examination. Meanwhile, when confirmed as a diseased point, it is treated by injecting a liquid agent or so, wherein the needle tool is also used for this purpose. The needle tool is sharpened at its tip because to be inserted in a body interior. In the event the needle tool goes into contact with the balloon in an inflated state, the balloon results into burst. Accordingly, there is a need to operate the needle tool in a manner not to contact the balloon.
JP-A-5-56912 discloses a structure whose balloon is not to be damaged by a needle tool, in a structure that an ultrasonic endoscope is fit with a balloon on a distal hard portion thereof in a region where an ultrasonic transducer is arranged, and provided with a treatment equipment lead-out hole in a position rear of the balloon-fit area so that the needle tool can be projected out of the treatment equipment lead-out hole thereby performing a treatment, such as cell sampling. In JP-A-5-56912, a treatment equipment rising device is provided in the distal hard portion so that the rising device can regulate the angle of the needle tool projecting out of the treatment equipment lead-out hole into a direction not to contact the inflated balloon.
In JP-A-5-56912, the rising device for regulating the direction of the treatment equipment is provided in the interior of the treatment equipment lead-out hole. The treatment equipment lead-out hole is spaced from the arrangement region of the ultrasonic transducer because it is arranged rear of the balloon-fit area. Here, in order to ensure a safe treatment with the needle tool, the needle tool is arranged to be monitored through the endoscopic viewing means in the stage before inserted in a body interior, and monitored through the ultrasonic examining means after inserted in the body interior. However, where the treatment equipment lead-out hole and the ultrasonic transducer are spaced in position, there is a need to increase the region where the needle tool is to be monitored by the endoscopic viewing means wherein the needle tool is not allowed to be inserted in a body interior until reaching the scanning range of the ultrasonic transducer. This increases the distance required for the needle tool to reach from the treatment equipment lead-out hole to an insertion point into a body interior, during which the needle tool at its tip is placed in a free state without being given any guide. This problematically results in a lowered shootability of the treatment equipment to a diseased point, etc.